The present invention relates to a laminated heat exchanger manufactured by alternately laminating tube elements and fins, in which corrosion of the passage plates provided at the two ends in the direction of lamination is prevented.
Laminated heat exchangers in the prior art are manufactured by alternately laminating tube elements each constituted by bonding face-to-face formed plates whose main constituent is aluminum, and fins. For instance, as disclosed in Japanese Unexamined Patent Publication No. H7-294175, tube elements each having a pair of tanks provided at one side and a U-shaped passage communicating between the pair of tanks are laminated alternately with fins over a plurality of levels. The tanks in adjacent tube elements are connected to form two tank groups extending in the direction of lamination. One of the tank groups is partitioned approximately in the middle to be divided into a first communicating area and a second communicating area and the other tank group is in communication throughout with no partitioning. Also intake/outlet passage plate having an intake portion, through which a heat exchanging medium flows in and an outlet portion, through which the heat exchanging medium flows out, is bonded to a flat plate constituting the outermost tube element in the direction of lamination at the end portion of the second communicating area in the direction of lamination.
In addition, the intake portion is made to communicate with the first communicating area via a communicating pipe, whereas the second communicating area is made to communicate with the outlet portion.
A laminated heat exchanger structured as described above is manufactured through brazing in a furnace, with a flat plate employed at an outermost tube element in the direction of lamination, a passage formation plate for changing the positions of the intake portion and the outlet portion bonded on the outside of the flat plate and a jig or the like employed to fix the entire assembly. During this furnace brazing, an aluminum alloy such as #3003, which is not clad with the brazing material emerges in the areas that are in contact with the jig, preventing contact with the jig supporting the laminated heat exchanger.
In a laminated heat exchanger manufactured through furnace brazing, the brazing material is not clad on the outside of the flat plate (also referred to as an end plate) of the outermost tube element with which the jig comes in contact as explained above, thus exposing a core material constituted of, for instance, aluminum alloy #3003. In addition, as in the example of the prior art described above, a core material (such as aluminum alloy #3003) is exposed in a similar manner on the outside of the intake/outlet passage plate.
When the aluminum alloy #3003 constituting the core material is directly exposed in this manner, since the core material does not achieve any sacrificial corrosion, a problem of poor anticorrosion properties arises. The generally practiced solutions to the problem include using a surface clad with a brazing material (aluminum alloy #4004) to come in contact with the jig to prevent the core material from corroding, and increasing the thickness of the plate to improve its anticorrosion properties. However, when the surface, clad with a brazing material, comes in contact with the jig, as in the former case, the process of separating them must be added into the production work, and increasing the plate thickness leads to an increase in the price and an increase in the weight of the laminated heat exchanger.